I kind of don't like the assumption that "anime conventions" should only allow anime-related cosplay and events. It seems snobby to me, and I don't think snobby is what we're going for. If anime conventions were only for anime, we'd have to do away with Star Wars, Firefly, Doctor Who, Star Trek, steampunk, comic book, video games, and classic fantasy cosplayers as well, and that would make most cons I've been to look pretty dismal. ETA: Not to mention Lolita and J-pop/J-rock cosplays as well, which aren't strictly anime themselves.
There are a lot of different fandoms and interests that crossover readily among certain groups of people. Although I don't particularly like the direction steampunk is going, I can certainly appreciate the costumes people put time and money into to wear at my anime convention. Also, steampunk fans don't really have a place to go to embrace their fanliness right now. Once there are more steampunk balls and conventions, I'll expect to see a little less steampunk happening at anime conventions.
But as far as I'm concerned, the more the merrier at anime conventions. I'm happy its become such a great melting pot of different interests, opinions, attitudes, and costuming styles. It's growing more and more every year.
I am the phreaking Phunbaba!!!
Planned: Rumi from Perfect Blue. (A-Kon 22)
Completed: Misato Katsuragi. (A-Kon 21)